Backend efficiency & consistency pass

- Rewrite get_all_tags() with SQL unnest instead of loading all notes
- Consolidate convert_note_to_task/convert_task_to_note to single-session ops
- Add search_notes_for_context() with single OR-keyword query for build_context()
- Drop selectinload from list_conversations(), use correlated subquery for message_count
- Add set_settings_batch() for single-transaction multi-setting upserts
- Extract get_installed_models() shared helper into services/llm.py
- Delete services/tasks.py pass-through wrapper; routes/tasks.py imports from services.notes
- Add B-tree indexes on notes.title and conversations.updated_at (migration 0007)
- Add logging to services/notes.py, services/chat.py, services/settings.py
- Safe Conversation.to_dict() when messages relationship is not loaded

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/fabledassistant/services/chat.py

@@ -1,3 +1,4 @@
+import logging
 from datetime import datetime, timezone
 
 from sqlalchemy import func, select
@@ -8,6 +9,8 @@ from fabledassistant.models.conversation import Conversation, Message
 from fabledassistant.services.llm import generate_completion
 from fabledassistant.services.notes import create_note
 
+logger = logging.getLogger(__name__)
+
 
 async def create_conversation(title: str = "", model: str = "") -> Conversation:
     async with async_session() as session:
@@ -35,20 +38,40 @@ async def get_conversation(conversation_id: int) -> Conversation | None:
 
 async def list_conversations(
     limit: int = 50, offset: int = 0
-) -> tuple[list[Conversation], int]:
+) -> tuple[list[dict], int]:
     async with async_session() as session:
         total = await session.scalar(
             select(func.count(Conversation.id))
         ) or 0
 
+        # Subquery for message count — avoids loading all messages
+        msg_count = (
+            select(func.count(Message.id))
+            .where(Message.conversation_id == Conversation.id)
+            .correlate(Conversation)
+            .scalar_subquery()
+        )
+
         result = await session.execute(
-            select(Conversation)
-            .options(selectinload(Conversation.messages))
+            select(Conversation, msg_count.label("message_count"))
             .order_by(Conversation.updated_at.desc())
             .limit(limit)
             .offset(offset)
         )
-        conversations = list(result.scalars().all())
+
+        conversations = []
+        for row in result.all():
+            conv = row[0]
+            d = {
+                "id": conv.id,
+                "title": conv.title,
+                "model": conv.model,
+                "message_count": row[1],
+                "created_at": conv.created_at.isoformat(),
+                "updated_at": conv.updated_at.isoformat(),
+            }
+            conversations.append(d)
+
         return conversations, total
 
 
@@ -149,6 +172,7 @@ async def summarize_conversation_as_note(
         {"role": "user", "content": "\n\n".join(conv_text)},
     ]
 
+    logger.info("Summarizing conversation %d with model %s", conversation_id, model)
     summary = await generate_completion(prompt_messages, model)
 
     title = conv.title or "Conversation Summary"